蓝桥小白赛1

👩‍🏫 地址

1. 蘑菇炸弹

👩‍🏫 蘑菇炸弹
在这里插入图片描述

🎉 AC code

import java.util.Scanner;public class Main
{public static void main(String[] args){Scanner sc = new Scanner(System.in);int n = sc.nextInt();int[] a = new int[n];for (int i = 0; i < n; i++)a[i] = sc.nextInt();int cnt = 0;for (int i = 1; i < n - 1; i++)if (a[i] >= a[i - 1] + a[i + 1])cnt++;System.out.println(cnt);}
}

2. 构造数字

👩‍🏫 构造数字
在这里插入图片描述

🎉 AC code

import java.util.Scanner;public class Main
{public static void main(String[] args){Scanner sc = new Scanner(System.in);int n = sc.nextInt();int m = sc.nextInt();char[] ans = new char[n];for (int i = 0; i < n; i++){if (m > 0){if (m >= 9){ans[i] = (char) (9 + '0');m -= 9;} else{ans[i] = (char) (m + '0');m = 0;}} else{ans[i] = '0';}}
//		System.out.println(ans[0]);System.out.println(String.valueOf(ans));}
}

3. 小蓝的金牌梦

👩‍🏫 题目地址

在这里插入图片描述

🎉 AC code

import java.util.HashSet;
import java.util.Scanner;public class Main
{static int N = 100010;static boolean[] st = new boolean[N];static int[] p = new int[N];static int cnt = 0;static void init(int n){for (int i = 2; i <= n; i++){if (!st[i])p[cnt++] = i;for (int j = 0; p[j] <= n / i; j++){st[p[j] * i] = true;if (i % p[j] == 0)break;}}}public static void main(String[] args){Scanner sc = new Scanner(System.in);int n = sc.nextInt();init(n);int[] a = new int[n + 1];long[] s = new long[n + 1];s[0] = 0;for (int i = 1; i <= n; i++){a[i] = sc.nextInt();s[i] = s[i - 1] + a[i];}long ans = Long.MIN_VALUE;for (int i = 0; i < cnt; i++){int len = p[i];for (int j = 0; j + len <= n; j++){long x = s[j + len] - s[j];ans = ans < x ? x : ans;}}System.out.println(ans);}
}

4. 合并石子

在这里插入图片描述

⭐ 思路

找规律：最基础的三个a.b,c，不管是 a * b + (a+b)* c还是另一种选择a * c + (a+c) * b，不难发现两者完全相等（前缀和）

🎉 AC code

import java.util.*;
import java.math.BigInteger;
// 1:无需package
// 2: 类名必须Main, 不可修改public class Main {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();long[] a = new long[n];for (int i = 0; i < n; i++) a[i] = sc.nextInt();BigInteger ans = new BigInteger("0");BigInteger sum = new BigInteger(String.valueOf(a[0]));for (int i = 0; i < n - 1; i++) {ans = ans.add(sum.multiply(new BigInteger(String.valueOf(a[i+1]))));sum = sum.add(new BigInteger(String.valueOf(a[i + 1])));}System.out.println(ans);sc.close();}
}